1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to processing images, and more particularly, to processing a red/green/blue (RGB) image signal to display on a plasma display panel (PDP).
2. Description of the Related Art
A related art PDP divides one 16.7 ms frame into eight subfields and gives the first to eighth subfields the brightness weights of 1, 2, 4, 8, 16, 32, 64, and 128 to represent 256 graylevels. However, when an image signal is displayed on the PDP in this manner, problems such as false contour, motion blur, or rounding error are frequently generated.
FIGS. 1 to 2B explain the problems of a related art image signal processor.
Referring to FIG. 1, pixels a, b, c, d, and e have a graylevel 127, and pixels f, g, h, i, and j have a graylevel 128. In other words, the pixels a, b, c, d, and e have a graylevel 127 as the first to seventh subfields SF1, SF2, . . . , SF7 are given the weights 1, 2, 4, 8, 16, 32, and 64, and the pixels f, g, h, i, and j have a graylevel 128 as the eighth subfield SF8 is given weight 128.
The human eye tracks as indicated in phantom lines in FIG. 1 when a pattern having graylevels 127 and 128 move leftward with the speed of 6 pixels/frame. Therefore, the brightness is perceived as illustrated in FIG. 2B, which is varied from the original state as illustrated in FIG. 2A. In FIGS. 2A and 2B, the vertical axis represents the graylevels, and the horizontal axis represents the locations of the pixels.
The movement range of the human eye stays in the non-illuminating subfields SF1, SF2, . . . , SF7 of the pixels f, g, h, i, and j, and in the non-illuminating subfield SF8 of the pixels a, b, c, e, and d, causing the human eye to perceive the graylevels of the original image differently. This appears in a contour form when the gradually-changing pattern moves fast, such as the case of skin color, and thus is often called a ‘pseudo contour.’
Furthermore, a motion blur may be generated when the contrast is deteriorated due to the influence of the illuminating subfields of the original image on the neighboring pixels. If the subfields are moved to compensate for the pseudo contour or motion blur, rounding error is generated due to fractional-number errors. As a result, the PDP has image degradation.